(a) Technical Field
The present disclosure relates to a separation system for a waste foundry sand binder. More particularly, it relates to a system for separating a binder attached to waste foundry sand using ultrasonic waves.
(b) Background Art
A foundry sand containing silica as a main component, and having excellent fire resistance, is widely used as a material for a casting mold used in a foundry. In general, a binder containing various additives and water are added to the foundry sand, which preferably has a grain size of 20 to 70 mesh. The mixture is then placed in a mold having a pattern on the surface, and it is hardened by various methods, to thereby form a casting mold.
When a cast product is produced using the thus formed casting mold, the binder is carbonized on the surface of the foundry sand (e.g. by the heat of molten metal). Thereafter, the foundry sand becomes waste foundry sand.
The waste foundry sand, however, has reduced fire resistance, air permeability, and moldability. Therefore, various techniques for recycling the waste foundry sand have been developed.
The conventional methods for recycling the waste foundry sand are generally divided into two categories.
According to a first conventional recycling method, the waste foundry sand is physically collected, sorted and separated for different uses, such as flux for copper smelting, as a subsidiary material for brick production, as a material for embankment, as a subsidiary material for cement production, etc.
According to a second conventional recycling method, a high-temperature treatment (at 700° C. or higher) is performed to oxidize (or burn) the binder attached to the surface of the waste foundry sand, and the binder on the surface is struck with a hard object (impact surface treatment) or dropped to a grinding stone (grinding surface treatment) to separate the binder from the surface of the waste foundry sand.
However, in this second method, a large amount of fuel is required to burn the binder and, after burning, greenhouse gases such as carbon dioxide are released into the atmosphere. Moreover, the impact and grinding surface treatments that are used cause crushing of the waste foundry sand and excessive atomization, thereby reducing the recovery rate. Therefore, it takes a long time to remove the binder from the surface of the waste foundry sand, there is a decrease in recovery, and significant operating expenses are incurred using this method.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.